Air-hydraulic booster



C. H. HART AIR-HYDRAULIC BOOSTER Filed June 12, 1952' INVENTOR.

BY Q. 7

Unit States AIR-HYDRAULIC BOOSTER Charles H. Hart, Detroit, Mich.

Application June 12, 1952, Serial No. 293,220 Claims. (Cl. Gil-54.6)

This invention relates to improvements in an air-hydraulic booster unitof the type comprising a pneumatically actuated piston and a hydraulicram or plunger connected for recriprocation in unison, the ram orplunger having a smaller volume of displacement than the piston andbeing reciprocable Within a hydraulic chamber, thereby to displace fluidfrom the chamber at increased pressure with respect to actuating airpressure applied to the piston.

An important object of the present invention is to provide an improvedbooster unit of the aforesaid nature which is particularly simple andeificient in structure and operation and which provides improvedautomatic means for replenishing fluid within the hydraulic chamber uponeach retraction stroke of the ram or plunger.

Another object is to provide a booster unit of the foregoing naturewherein the reciprocable ram or plunger is movable toward an inlet porton the forward or fluid displacement stroke and is movable from theinlet port on the retraction stroke. A plunger type valve extendinglongitudinally in the direction of reciprocation and adapted at one endto seat at the inlet port to close the same is slidably mounted on theram or plunger. A projection on the ram or plunger is arranged to engageand move the valve from the inlet port to open the latter uponretraction of the plunger to a predetermined position adjacent its limitof retraction movement. Upon movement of the plunger beyond saidpredetermined position in the direction toward the inlet port, the valveis released from said projection for movement toward the inlet port toseat thereat, spring means being employed to urge the valve yieldinglyto the seated position. Thus throughout continued movement of the ram orplunger toward the inlet port, the latter is maintained closed by thevalve and fluid displaced by the ram or plunger is forced undermagnified pressure from the hydraulic chamber. However upon completionof each retraction movement, the inlet port is open to replenish fluidlost from the hydraulic system during the preceding operation.

Another and more specific object of the invention is to provide aparticularly compact and eflicient booster unit of the characterdescribed having an axially reciprocable plunger movable toward and fromthe inlet port as aforesaid and provided with an axially extending boreopening toward the inlet port and having said plunger type valveslidably seated therein. The valve in turn is provided with an axiallyextending bore opening at one end into the bore of the plunger. Theother end of the plunger type valve is adapted to seat at the inlet portas aforesaid to close the latter. Secured to the ram or plunger is aspring guide which extends axially into the bore of the valve toposition a spring coiled around the guide under compression between theplunger and valve to urge the latter yieldingly toward the inlet port toseat thereat. Spaced apart slightly less than the distance of retractionmovement when the plunger is at its limit of movement toward the inletport are cooperating shoul- 2,765,625 Patented Oct. 9, 1956 ders on thevalve and plunger arranged to abut each other upon retraction of theplunger substantially to its limit of movement, thereby to move thevalve from the inlet port to open the latter upon completion of theretraction stroke.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

Fig. 1 is a longitudinal median section.through an airhydraulic boosterunit embodying the present invention, showing the hydraulic ram orplunger at the limit of its work or displacement stroke.

Fig. 2 is a view similar to Fig. 1 but showing the ram or plunger at thelimit of its retraction stro re.

Fig. 3 is a section taken in the direction of the arrows substantiallyalong the line 33 of Fig. 2.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to the drawings, a particular embodiment of the presentinvention is shown comprising by way of example a two part housingincluding a hydraulic cylinder 1i and a pneumatic cylinder 11 arrangedcoaxially end to end with their bores opening into each other.Reciprocable within the cylinder 16 is a hydraulic ram or plunger 12which is adapted to extend substantially the entire length of thecylinder 10 and rearward partially into the cylinder ii. The diameter ofthe rear end of the plunger 12 is reduced to provide a seat 13 for apiston indicated generally by the numeral 14 and reciprocable within thecylinder 11. The piston 14 comprises a center plate 15 spaced fromforward and rearward outer plates 16 and 17 respectively by forward andrearward piston cup packings 1S and 19 respectively. The latter aresupported by their corresponding plates 16 and 17 so as to conformclosely to the interior of the air cylinder 11 during pneumaticactuation as discussed below. The forward plate 16 is held snuglyagainst the shoulder at the forward end of the reduced plunger portion13 by a lock washer 2i) and nut 21 screwed on an externally threadedrear end of the reduced ram portion 13.

The hydraulic and air cylinders 10 and 11 are separated by forward andrearward packing rings 22 and 23 located snugly around the ram orplunger 12 within a rearward enlargement of the bore for the hydrauliccylinder lit The rings 22 and 23 are reinforced by annular supportglands 24 and 25 respectively and are spaced by an annular drain member26. The inner and outer circumferences of the member 26 are providedwith annular drain grooves connected by one or more radial ducts 27, theouter drain groove being in turn in communication with a dischargeconduit 28 which extends radially through the housing portion 11 todischarge hydraulic fluid that might leak rearward from the cylinder 10.Secured to the forward wall of the air cylinder 11 by screws 29 is anannular retaining gland 3t) overlying the packing 23 to hold the same inposition.

By the structure described thus far, the piston 14 and ram 12 arereciproc-able as a unit, so that pneumatic pres= sure applied to drivethe piston 14 forward is magnified in the hydraulic cylinder inaccordance with the ratio of the cross sectional areas of the piston 14to the ram or plunger 12. Pneumatic actuation of the piston .14 isachieved by a high pressure port 31 in a rear end closure plate 32,which is secured to the cylinder 11 by bolts 33,

and by a return port 34 in the sidewall of the cylinder 11 forward ofthe limit of forward movement of the piston 14. The ports 31 and 34 areconnected to conduits 35 and 36 respectively within a pneumatic circuit,whereby the piston 14 is selectively driven forward to the position ofFig. l by introducing high pressure air through port 31, or retracted tothe rearward position of Fig. 2 by introducing air pressure through port34 when conduit 35 is connected to exhaust.

The forward end of the hydraulic cylinder is closed by a forward endclosure plate 37 secured to the cylinder 10 by a plurality of bolts 38.The plate 37 is provided with a radial inlet conduit 39 in communicationat its inner end with an axial inward opening hydraulic port 40. Theouter end of the conduit 39 is connected with a conduit 41 which in turnis connected with a source of hydraulic fluid, as for example a watersupply under ordinary city water pressure. A radial outlet conduit 42 inthe forward end closure plate 37 is connected at its inner end with anaxially inward opening hydraulic discharge port 43 and is connected atits outer end with a conduit 44 which extends to the machine or deviceto be hydraulically actuated, such as a spot welding gun, for example.O-rings 45 and 46 seated within radially outward opening annular groovesin inner offset portions of the rear and forward end closure plates 32and 37 respectively snugly engage the adjacent inner walls of thecylinders 11 and 10 respectively to provide fluid tight seals thereat.

The hydraulic inlet port 40 opens into the cylinder 10 coaxially withthe ram or plunger 12 and is adapted to be closed by the conicallytapered forward end of a plunger type valve 47 when the latter ispressed forward, as described below. The stem of the valve 47 extendscoaxially rearward into a bore 48 within the ram or plunger 12 and isslidable therein to permit forward movement of the plunger 12 to thelimit of movement, Fig. l, as determined by abutment between the glandand piston plate 16. The rear end of the bore within the ram or plunger12 is closed by a screw plug 49 which supports a spring guide 50extending coaxially forward within a rearwardly opening bore 51 in thevalve 47 The latter is yieldingly urged forward to the seated positionto close the inlet by means of a coil spring 52 which extendslongitudinally within the bore 51 and around the guide and is undercompression between the forward end of the bore 51 and a rear springretaining washer 52a. The latter is located around the guide 50 near itsjuncture with the plug 49 and is spaced from the plug by a washer 53.

In order to retract the valve 47 from the port 40, the valve 47 isprovided intermediate its ends with a radial shoulder 54 adapted to beabutted by a generally annular mating shoulder 55 of the plunger 12extending radially inward around the valve 47 adjacent the forward endof the plunger 12. When the piston 14 is at its forward limit ofmovement, Fig. 1, the shoulders 54 and 55 are spaced apart a distanceslightly less than the maximum rearward travel permitted to the piston14 and plunger 12. Accordingly, just before the piston plate 17 abutsthe forward surface of the rear end plate 32, the shoulder 55 moves intoabutment with the shoulder 54, causing retraction of the valve 47 fromits seated position at the hydraulic inlet port 40 and opening of thelatter upon continued rearward movement of the plunger 12. The spring 52is dimensioned so as to urge the shoulder 54 yieldingly forward towardthe shoulder 55 at all positions of the plunger 12. Accordingly uponforward movement of the piston 14 from the rearmost or retractedposition, Fig. 2, the valve 47 will move forward with the plunger 12 andshoulder 55 until the tapered end of valve 47 seats at and closes theport 40, whereupon the shoulder 55 continues forward of the position ofabutment with the shoulder 54. Hydraulic pressure in the forward end ofcylinder 10 and the bore 51 of valve 47 is equalized by means of one ormore ports 56 extending axially in the annular shoulder 55 and one ormore radial ports 57 through the valve 47.

During normal operation of the booster unit, the duct system 39 through44 and the portion of the cylinder 10 not occupied by the plunger 12 aremaintained full of fluid. During a forward work or pressure stroke ofthe ram or plunger 12 and after the valve 47 has seated itself at theport 40 to close the same, the fluid displaced from the cylinder 10 bythe plunger 12 is forced under pressure to the work stroke via conduit44. Upon completion of the work stroke, the plunger 12 is retracted andfluid within the duct system 44 backs from the work to fill the cylinder10. When the plunger 12 almost reaches the rearward limit of theretraction stroke as aforesaid, the shoulders 55 and 54 abut each other,causing retraction of valve 47 and opening of inlet port 40. In theevent that hydraulic fluid has been lost from the circuit during thepreceding work stroke, the lost fluid is now replenished via port 40. Onthe next work stroke, fluid is momentarily forced back through port 40until forward movement of shoulder 54 permits the forwardly springpressed valve 47 to seat at and close port 40. Thereafter the workstroke is repeated as above.

I claim:

1. In a pressure booster, a low pressure cylinder, a high pressurecylinder, a piston reciprocal in the low pressure cylinder, a tubularplunger reciprocal in the high pressure cylinder and extendingrearwardly therefrom into the low pressure cylinder, said plunger beingsecured to the piston to reciprocate therewith, a fluid inlet port inthe forward portion of the high pressure cylinder, a valve seat aroundsaid port, a plunger type valve shiftable forwardly against said seat toclose said port, a tubular stern connected to said valve to shifttherewith and extending rearwardly therefrom into the bore of saidplunger and opening rearwardly thereinto, a spring guide secured to saidpiston to reciprocate therewith and extending for wardly therefrom intothe bore of said stem through the rear end thereof, a coil spring withinthe bore of said stem and around said guide and under compressionbetween said piston and valve to urge the latter forwardly to close saidinlet port, mating shoulders on said stern and plunger cngageable tomove said valve from said valve seat upon rearward shifting of saidpiston to adjacent its limit of rearward movement, a radial duct throughthe sidewalls of said stem adjacent the forward end thereof andconnecting the bore of said stem with said high pressure cylinder, fluidpassage means extending between the juxtaposed walls of said plunger andstem and connecting said radial duct with said forward portion of saidhigh pressure cylinder when the plunger is at its limit of forwardmovement, and a fluid outlet port in said forward portion of the highpressure cylinder.

2. In a pressure booster, a low pressure cylinder, a high pressurecylinder, a piston reciprocal in the low pressure cylinder, a tubularplunger reciprocal in the high pressure cylinder and extendingrearwardly therefrom into the low pressure cylinder, said plunger beingsecured to the piston to reciprocate therewith, a fluid inlet port inthe forward portion of the high pressure cylinder, a valve seat aroundsaid port, a plunger valve shiftable forwardly against said seat toclose said port, a tubular stem connected to said valve to shifttherewith and extending rearwardly therefrom into the bore of saidplunger and opening rearwardly thereinto, the forward end of the bore ofthe tubular stem being closed by said valve, a spring guide secured tosaid piston to reciprocate therewith and extending forwardly therefrominto the bore of said stem through the rear end thereof, a coil springwithin the bore of said stem and around said guide and under compressionbetween said piston and valve to urge the latter forwardly to close saidinlet port, mating shoulders on said stern and plunger engageable tomove said valve from said valve seat upon rearward shifting of saidpiston to adjacent its limit of rearward movement, said stem having aduct connecting its bore with the interior of said high pressurecylinder, axially extending fluid passage means between the juxtaposedwalls of said plunger and stem and connecting said duct with saidforward portion of said high pressure cylinder when the plunger is atits limit of forward movement, and a fluid outlet port in said forwardportion of the high pressure cylinder.

3. A pressure booster having low and high pressure cylinders, the formerbehind the latter, a piston reciprocal axially within the low pressurechamber, a tubular plunger shiftable axially Within said cylinders andconnected to said piston, a fluid inlet port in the forward portion ofthe high pressure chamber, a valve seat around said port, a plunger typevalve shiftable forwardly against said seat to close said port, atubular stem connected to said valve to shift therewith and extendingrearwardly therefrom into the bore of said plunger and openingrearwardly thereinto, said valve closing the forward end of the bore ofsaid stem, said stern substantially filling the bore of said plungerwhen said piston is at its limit of forward movement, a spring guidesecured to said piston to reciprocate therewith and extending forwardlytherefrom into the bore of said stem through the rear opening thereof,said spring guide substantially filling the bore of said stern when saidpiston is at its limit of forward movement, a coil spring around saidguide and compressible Within the bore of said stem between said pistonand valve to urge the latter forwardly to close said port, said plungerhaving a portion engageable with a portion on said stem to move saidstem and valve rearwardly to open said port upon predetermined rearwardmovement of said plunger, said stern having a radial duct therethroughopening into the bore thereof, axially extending fluid passage meansbetween the juxtaposed portions of said stern and plunger and connectingsaid radial duct with the forward portion of said high pressure cylinderwhen the plunger is at its forward limit of movement, and a fluid outletport in the forward portion of said high pressure chamber.

4. In a pressure booster, a low pressure cylinder, a high pressurecylinder, a piston reciprocal in the low pressure cylinder, a tubularplunger reciprocal in the high pressure cylinder and extendingrearwardly therefrom into the low pressure cylinder, said plunger beingsecured to the piston to reciprocate therewith, a fluid inlet port inthe high pressure cylinder, a valve seat around said port, a plungertype valve shiftable forwardly against said seat to close said port, atubular stem connected to said valve to shift therewith and extendingrearwardly therefrom into the bore of said plunger and openingrearwardly thereinto, a guide secured to said piston to reciprocatetherewith and extending forwardly therefrom into the bore of said stemthrough the rear end thereof, spring means engaging portions fixed withrespect to said valve and piston respectively and yieldingly urging saidvalve forwardly with respect to said piston to close said inlet port,means on said stem and plunger for moving said valve from said valveseat upon rearward shifting of said piston to adjacent its limit ofrearward movement, said stem having a duct connecting its bore with theinterior of said high pressure cylinder, fluid passage means extendingbetween the juxtaposed walls of said plunger and stem and connectingsaid duct with said high pressure cylinder when the plunger is at itslimit of forward movement, and a fluid outlet port in said high pressurecylinder.

5. In a pressure booster, a low pressure cylinder, a high pressurecylinder, a piston reciprocal in the low pressure cylinder, a tubularplunger reciprocal in the high pressure cylinder and extendingrearwardly therefrom into the low pressure cylinder, said plunger beingsecured to the piston to reciprocate therewith, a fluid inlet port inthe forward portion of the high pressure cylinder, a valve shiftableforwardly to close said port, a tubular stem connected to said valve toshift therewith and extending rearwardly therefrom into the bore of saidplunger and opening rearwardly thereinto, the forward end of said stembeing closed at a location adjacent and rearwardly of said valve, aspring guide secured to said piston to reciprocate therewith andextending forwardly therefrom into the bore of said stem through therear end thereof, a coil spring within the bore of said stem and aroundsaid gude and under compression between said piston and valve to urgethe latter forwardly to close said inlet port, means on said stem andplunger for moving said valve from said valve seat upon rearwardshifting of said piston to adjacent its limit of rearward movement, saidstern having a duct rearwardly of said location connecting the bore ofsaid stem with the interior of said high pressure cylinder, fluidpassage means extending between the juxtaposed walls of said plunger andstem and connecting said duct with said forward portion of said highpressure cylinder when the plunger is at its limit of forward movement,and a fluid outlet port in said forward portion of the high pressurecylinder.

References Cited in the file of this patent UNITED STATES PATENTS1,550,089 Mattingly Aug. 18, 1925 1,593,188 Mattingly July 20, 19262,305,638 Rockwell Dec. 22, 1942 2,536,140 Rockwell Jan. 2, 1951

